Method of attaching a functional element to a sheet metal part

ABSTRACT

The invention relates to a method of attaching a functional element to a sheet metal part. The functional element has a head part having a ring-shaped support surface and a tubular rivet section that is designed as self-piercing and that extends at the side of the support surface of the head part and away from said head part.

The present invention relates to a method of attaching a functionalelement to a sheet metal part, wherein the functional element has a headpart having a ring-shaped support surface and a tubular rivet sectionthat is designed as self-piercing and that extends at the side of thesupport surface of the head part and away from said head part, whereinthe support surface comprises a ring recess in the region of thetransition from the head part into the rivet section, the ring recesshaving a ring surface inclined with respect to a longitudinal axis ofthe functional element, wherein the ring recess has its greatest depthadjacent to the rivet section, and wherein features providing securityagainst rotation are optionally provided, such as security againstrotation noses, that are located in the region of the ring recess and/orin the region of the transition of the ring recess into the rivetsection and that selectively divide the ring recess into individualfields distributed about the longitudinal axis of the functionalelement, wherein the sheet metal part is supported on a perforated diethat has a bore whose diameter at least substantially corresponds to theouter diameter of the rivet section or is somewhat larger than it,wherein the functional element is pressed onto the sheet metal partsupported on the perforated die such that a panel slug is punched out ofthe sheet metal part by means of the rivet section.

Such a method of attaching a functional element to a sheet metal partand the functional element itself are described, for example, in WO02/081145 A2. The method described in this document is a classicalriveting method that substantially takes place in two steps using twodifferent dies: in a first step, a panel slug is first punched out of asheet metal part by means of the rivet section using a perforated die,whereby a punched hole is created that receives the functional elementand in particular its rivet section in a clamping manner. In a secondstep, the free end of the rivet section is then folded over or beadedover using a rivet die such that the sheet metal part is clamped firmlybetween the functional element and its beaded over rivet section. Sincethe functional element is directly reshaped, it is a rivet element.

In the field of connection elements which are mechanically attached tosheet metal parts on the production thereof, a distinction is generallymade between force fitting elements, on the one hand, and rivetingelements, on the other hand. With rivet elements, the rivet section ofthe element is directly deformed on the attachment to the sheet metalpart in the described manner, as a rule to form a rivet flange at thefree end of the rivet section, whereby the sheet metal part is heldfirmly between the rivet flange and a flange part of the rivet elementto provide a connection secure against rotation and against beingpressed out. Force fitting elements are characterized in contrast inthat they are not, at least not intentionally, deformed or at best veryminimally deformed at a sheet metal part during the attachment; thesheet metal part is rather itself deformed and brought into engagementwith shape features of the force fitting element, whereby the forcefitting element is fastened to the sheet metal part in a manner secureagainst rotation and against being pressed out.

Both the force fitting elements and the rivet elements are furthermoreknown in the form of self-piercing elements. The designationself-piercing is to be understood such that the corresponding elementpunches its own hole into a sheet metal part if a sufficient force isexerted onto the self-piercing element, for example by a press, by arobot or by a power-operated pair of tongs, which presses theself-piercing element toward the sheet metal part and the sheet metalpart is supported on a corresponding die on the side remote from theelement.

Although the riveting method descried in WO 02/081145 A2 has providedgood service, it would be desirable in various applications if it werepossible to be able to attach the functional element acting as a rivetelement there to a sheet metal part in a manner secure against rotationand against being pressed out using only one single machining step.

It is therefore the underlying object of the invention to furtherdevelop the method known from WO 02/081145 A2 of attaching a functionalelement acting as a rivet element to a sheet metal part such that themachining effort is reduced. The method should in particular serve forattaching a so-called RND rivet element of the company ProfilVerbindungstechnik GmbH and Co. Kg to a sheet metal part secure againstrotation and against being pressed out.

In accordance with the invention, a method of attaching a functionalelement to a sheet metal part that preferably has a thickness of morethan 3 mm is proposed to satisfy this object, wherein the functionalelement has a head part having a ring-shaped support surface and atubular rivet section that is formed as self-piercing and that extendsat the side of the support surface of the head part and away from thehead part, wherein the support surface comprises a ring recess having aring surface inclined with respect to a longitudinal axis of thefunctional element in the region of the transition from the head partinto the rivet section, wherein the ring recess has its greatest depthadjacent to the rivet section, and wherein features providing securityagainst rotation, for example, security against rotation noses, areoptionally provided that are located in the region of the ring recessand/or in the region of the transition of the ring recess into the rivetsection and that selectively divide the ring recess into individualfields distributed about the longitudinal axis of the functionalelement, wherein the sheet metal part is supported on a perforated diethat has a bore whose diameter at least substantially corresponds to theouter diameter of the rivet section or is somewhat larger than it,wherein the bore is surrounded at the end face of the perforated diefacing the sheet metal part by a ring nose that is raised with respectto a support surface of the perforated die and defines a planar circularring-shaped end surface, wherein the functional element is pressed ontothe sheet metal part supported on the perforated die such that a panelslug is punched out of the sheet metal part by means of the rivetsection and a portion of the sheet metal material that surrounds thepunched hole generated by the punching out of the panel slug isplastically pressed by means of the circular ring-shaped end face of thering nose into the ring recess while completely filling it, on the onehand, and is pressed in the region of the transition from the head partinto the rivet section radially into the rivet section, on the otherhand.

A kind of undercut in the form of a crease or constriction is thereforeproduced at the rivet section, on the one hand, on the attachment of thefunctional element to the component, said undercut receiving a portionof the plastically reshaped sheet metal material, whereby the functionalelement is held at the sheet metal part secure against being pressedout. In order, however, also to provide security against rotation in thedesired manner, a portion of the plastically shaped sheet metal materialis urged up to and into the ring recess, and indeed so far that the ringrecess is substantially completely filled by sheet metal materialdisplaced in this manner such that an unintentional rotation of thefunctional element is precluded, in particular when features providingsecurity against rotation, such as security against rotation noses, areprovided that are located in the region of the ring recess and/or in theregion of the transition of the ring recess into the rivet section anddivide the ring recess into individual fields distributed about thelongitudinal axis of the functional element.

A component assembly manufactured using the method in accordance withthe invention and comprising the self-piercing rivet element and a sheetmetal part is thus characterized in that the sheet metal part has apunched hole having a shape corresponding to the shape of the rivetsection and in that the material of the hole margin extends, on the onehand, up to and into the ring recess while substantially completelyfilling it and, on the other hand, extends into a constriction or into acrease that is formed radially in the rivet section at the outerperiphery thereof.

The function of the perforated die is thus not only restricted to thepunching out of a punched hole suitable for receiving the rivet element;the sheet metal part is rather fastened to the rivet element after theproducing of the punched hole such that the rivet element contacts thesheet metal part secure against rotation and against being pressed out.It is particularly surprising that in the starting state before theattachment to the sheet metal part, the rivet element does not have tohave any features such as an undercut in the rivet section that couldensure the security against being pressed out or the resistance to beingpressed out. A high-quality security against being pressed out cannevertheless be achieved since, on the cutting out of the panel slugand/or on the attachment to the sheet metal part, that generally hastwice the strength value in comparison with the rivet element, the sheetmetal material deforms the softer rivet element and presses into it suchthat it is located in a ring-shaped crease or constriction that isformed at the shaft of the rivet section under the pressure of the sheetmetal material that is produced by the die. It is particularlysurprising that such a deformation of the rivet section, i.e. theformation of a constriction that extends radially into the rivetsection, also has to be reached when the sheet metal part has a smallerstrength than the element.

The method in accordance with the invention is substantially based onthe recognition not only to press the material of the sheet metal partthat surrounds the punched hole into the ring recess, but alsosimultaneously to press it into the rivet section to form a constrictiontherein. It has in particular been recognized that this is possible bymeans of a specially formed perforated die. The perforated die used inthe method thus has a ring nose at the end face facing the sheet metalpart that surrounds the bore of the perforated die and that is raisedwith respect to a support surface of the perforated die and inparticular defines a planar circular ring-shaped end surface. Unlike theperforated die used in the method described in WO 02/081145 A2, theperforated die in the method in accordance with the invention thereforedoes not have a ring lip that defines a peripheral burr that does nothave any radial extent; the ring nose of the perforated die used in themethod in accordance with the invention rather has a planar circularring-shaped surface that has a not insubstantial extent in the radialdirection.

It has namely been recognized in accordance with the invention that thesheet metal material that surrounds the punched hole produced by thepunching out of the panel slug cannot be laterally displaced when theperforated die contacts the sheet metal material via the planar circularring-shaped end surface as would otherwise be the case if the perforateddie had a burr-like ring lip in accordance with the model of WO02/081145 A2 since in this case the ring lip would press into the sheetmetal material with the burr to the front and would laterally displacesaid sheet metal material. In contrast to his, a compression stress canbe built up over the planar end surface of the ring nose of theperforated die that is used in the method in accordance with theinvention in the sheet material that surrounds the punched hole producedby the punching out of the panel slug until the material exceeds theflow limit and starts to flow plastically such that it not onlypenetrates into the ring recess at continued pressure, but ratherproduces a constriction that is adjacent thereto in the rivet section ofthe rivet element and that is then covered by the sheet metal material.

Since a portion of the sheet metal material thus flows both into thering recess and into the constriction of the rivet section, theperforated die presses into the sheet metal material with the planarcircular ring-shaped end surface of the ring nose at the front and in sodoing so-to-say pushes the sheet metal material in front of it, wherebythe sheet metal part undergoes a ring-shaped cross-sectional weakeningadjacent and about the free end of the rivet section. A perforated dieshould accordingly be used as the perforated die in accordance with apreferred embodiment of the method whose circular ring-shaped endsurface of the ring nose has a radial extent that correspondsapproximately to half the thickness of the sheet metal part and/or thatis smaller than the radial extent of the ring recess, but is larger thanhalf the radial extent of the ring recess. The displaced material volumethus extends decisively in the radial direction, whereby it can beensured that no shear effects occur in the sheet metal part in theregion around the punched hole.

In order to be able to fill both the ring recess and the constriction ofthe rivet section with sheet metal material, it can furthermore proveadvantageous in accordance with a further embodiment if a perforated dieis used as the perforated die whose ring nose has a volume thatsubstantially corresponds to the volume of the ring recess of thefunctional element. The volume of the ring nose in particular does nothave to be substantially larger than the volume of the ring recess sincethe free end of the rivet section is compressed somewhat as part of thepunching process and is consequently pressed part in the radialdirection. This radial widening of the rivet section thus so-to-saycompensates the volume of the constriction such that it is sufficient ifthe ring nose has a volume that substantially corresponds to the volumeof the ring recess of the functional element.

The invention will be explained in more detail in the following withreference to the enclosed drawings, where

FIGS. 1 to 3 show a sequence of snapshots during the carrying out of themethod in accordance with the invention; and

FIG. 4 shows a detail from FIG. 3 in an enlarged representation.

FIG. 1 shows in an axial section a so-called RND rivet element 10 of thecompany Profil Verbindungstechnik GmbH and Co. KG. wherein the element10 is sectioned in an axial plane that comprises the middle longitudinalaxis 12 of the element 10. The element 10 shown is fastened to a sheetmetal part 14 using the method in accordance with the invention.

The functional element 10, that is configured as a nut element here, hasa head part 18 having a ring-shaped support surface 16 and a tubularpunching and rivet section 20 located at the side of the support surface16 of the head part 18. In the region of the transition from the headpart 18 to the rivet section 20, the support surface 16 comprises a ringrecess 22 having a ring surface 24 inclined with respect to thelongitudinal axis 12 of the functional element 10, wherein the ringrecess 22 has its greatest depth in the axial direction of the rivetelement 10 adjacent to the rivet section 20 and the inclined ringsurface 24 runs out in a further ring-shaped support surface region 27that lies in a radial plane and that itself merges into a roundedportion 21 or chamfer of the head part 18.

In this example, features providing security against rotation in theform of security against rotation noses 26 are provided in the region ofthe ring recess 22, with the security against rotation noses 26extending in the radial direction and bridging the ring recess 22. Inthis example, a total of six such security against rotation noses 26 areprovided that divide the ring recess 22 accordingly into six fieldsfollowing one another about the longitudinal axis 12. Fewer than six ormore than six such security against rotation noses 26 can be providedand the noses 26 can additionally, if desired, also be provided inraised form in the region of the transition of the ring recess 22 intothe rivet section 20. This is, however, not necessary and can alsoresult in complications in the attachment of the element so that suchsecurity against rotation noses have been omitted in thisrepresentation.

The ring-shaped region of the ring-shaped support surface 16 that standsin a plane perpendicular to the longitudinal axis 12 and that ispreferably not interrupted by security against rotation features 26 istherefore located around the ring recess 22.

The functional element 10 in this example has a center bore 28 that isprovided with an internal thread 30. The head part 18 additionally has aring-shaped cut-out 32 that defines a cylindrical region 34 of the headpart 18 that is surrounded by a ring-shaped pressure surface 36. Thefunctional element 10 does not have to be configured as a nut element.Instead, the cylindrical region 34 could merge over the ring surface 38into a shaft part that would extend upwardly in the representation inaccordance with FIG. 1 so that a bolt element is present. The functionalelement 10 could also have other functions. The bore 28 could, forexample, be configured as a cylindrical support surface for a rotatablesupport of a shaft or are realized as a clip mount to receive a clipfastening. If the element 10 is provided with a shaft part, the shaftpart cannot only be provided with a threaded cylinder, whereby a boltelement is present, but the shaft part could have a cylindrical supportsurface, e.g. for a rotatable support of a lever, or it could, forexample, be provided with a ring groove to receive a clip. What isimportant is that the ring surface 36 is configured as a pressuresurface so that a pressure in the longitudinal direction of thelongitudinal axis 12 by means of a suitable tool, here shown by 40, canbe exerted onto the pressure surface 36 to bring the element 10 into thesheet metal part 14 without the forces exerted on the functional element10 resulting in an impermissible deformation of the functional element10. It can additionally be seen from FIG. 1 that the tubular rivetsection 20 has an internal diameter that is considerably larger thanthat of the bore 28 or than that of the outer diameter of the thread 30and that the free end face of the tubular rivet section 20, i.e. thelower end in FIG. 1, is equipped with punching and rivet features thatwill be explained in more detail below.

A perforated die 42 is located beneath the sheet metal part 14 in FIG.1, wherein the tool 40 and the perforated die 42 normally lie oppositeone another and are provided aligned with one another in a station of aprogressive tool. This means that the longitudinal axis 12 of theelement 10 simultaneously represents the longitudinal axis of the tool40 and the longitudinal axis of the perforated die 42 and the perforateddie 42 is accommodated in a manner known per se in a lower plate of theprogressive tool and the upper tool 40 is moved in accordance with thedouble arrow 44 to accept a further functional element 10 in theposition shown on every upwardly directed movement and to provide theintroduction of the functional element into the sheet metal part 14 inthe manner to be explained in the following on every downwardly directedmovement. In another respect, the tool 40 and the perforated die 42could be arranged in a transfer press. The perforated die 42 would thenhave to be arranged in the lower tool of the press and the tool 40 isaccommodated in a setting head that is installed at an intermediateplate of the press or at the upper tool of the press. The perforated die42 could instead be installed on the intermediate plate of the press andthe tool 40 could be fastened to the upper tool of the press. Reversearrangements are also absolutely conceivable in which the lower tool 40is arranged beneath the perforated die 42, for example in the lower toolof the press or at the intermediate plate of the press while theperforated die would then have to be arranged at the intermediate plateor at the upper tool of the press.

It can furthermore be seen from FIG. 1 that the functional element 10 isaccommodated in a ring recess 46 of the tool 40 that has a ring-shapedshoulder 48 in the base region that presses toward the pressure surface36 of the functional element 36. The cylindrical region of the head part18 is accommodated in a further cylindrical recess 50 of the tool 40 andmerges over the ring shoulder 48 into the cylindrical recess 46. Thefree end of the tubular rivet section 20 of the functional element 10projects beyond the lower ring-shaped end face 52 of the tool, whereasthe ring-shaped support surface 16 of the functional element 10 lies inthe same radial plane as the lower ring-shaped end face 52 of the tool40.

The perforated die 42 has a center bore 54 that can merge in thedownward direction in FIG. 1 into a larger bore or can divergedownwardly to facilitate that a panel slug 66 that arises by means ofthe cooperation of the perforated die 42 and the rivet section 20 canfall out of the bore 54 of the perforated die 42, see FIG. 2. The bore54 is designed as slightly larger than the rivet section 20 so that itfits into the bore 54 with a small clearance. The bore 54 could, forexample, be approximately 0.01 mm larger in diameter in comparison withthe rivet section 20.

The bore 54 is surrounded at the side of the perforated die 42 facingthe sheet metal part 14 by a ring nose 80 that is raised with respect toa support surface 82 of the perforated die 42 and defines a planarcircular ring-shaped end surface 84. The ring nose 80 has the same innerdiameter as the bore 54. As can be seen from FIG. 1, the circularring-shaped end surface 84 of the ring nose 80 has a radial extent thatcorresponds to approximately half the thickness of the sheet metal part14. The circular ring-shaped end surface 84 of the ring nose 80 has aradial extent that is smaller than the radial extent of the ring recess22, but larger than half the radial extent of the ring recess 22. It canfurthermore be seen from FIG. 1 that the ring nose 80 has a volume thatsubstantially corresponds to the volume of the ring recess 22 of thefunctional element 10.

If now the upper tool 40 is moved downwardly in accordance with thedouble arrow 44, the rivet section 20 in accordance with FIG. 2 punchesa panel slug 66 out of the sheet metal part 14 that then falls throughthe preferably downwardly flaring bore 54 of the die 42 and can beremoved from the press. The punching of the sheet metal part 14 takesplace on the basis of shear forces that arise between the free end ofthe rivet section 20 and the inner margin of the ring nose 80 at theupper side of the die 42. Due to the huge force on the punching of thesheet metal part 14, not only the sheet metal part 14 is deformed, butthe free end of the rivet section 20 can also be compressed slightly inthe axial direction and can consequently be pressed slightly apart inthe radial direction, see FIG. 4, whereby a kind of undercut 47 isproduced at the rivet section 20 that is admittedly relatively small,but is very effective in the sense that a not inconsiderable resistanceto pressing out is ensured.

During the punching of the sheet metal part 14, the ring nose 80 alsopresses via its circular ring-shaped end surface 84 toward the lowerside of the sheet metal part 14 and there forms a recess 62 that extendsaround the rivet section 20 in the region of its free end. Due to thehuge forces that are introduced in this respect as reaction forces overthe circular ring-shaped end surface 84 into the material of the sheetmetal part 14, the material of the sheet metal part exceeds its flowlimit and starts to flow in the region around the rivet section 20,which has the consequence that the material displaced by the formationof the recess 62 is inter alia pressed into the undercut 47 at the rivetsection 20—provided it has formed—and even enlarges it, whereby thesheet metal part 14 is connected in a manner secured against beingpressed out to the element 10, see FIG. 3. At the same time, thematerial displaced by the formation of the recess 62 is pressed into thering recess 22 such that it fills it completely in accordance with FIGS.3 and 4, which becomes possible in that the volume of the ring nose 82substantially corresponds to the volume of the ring recess 22 or issomewhat larger than it. The material displaced in the ring recess 22 inthis respect tightly contacts the inclined ring surface 24 of the ringrecess 22 and fills the ring recess 22 completely such that the securityagainst rotation noses 26 are urged into the sheet metal material andthe functional element is thus fastened in a manner secure againstrotation at the sheet metal part 14. The engagement of the sheet metalmaterial into the forming undercut 47 also provides that a moreresistant engagement of the security against rotation noses in the sheetmetal material is ensured, which considerably increases the securityagainst rotation resistance. It must further be noted that the forcesthat are present on the attachment of the functional element to thesheet metal part substantially act between the ring-shaped pressuresurface 36 and the circular ring-shaped end surface 84 of the ring nosethat are opposite one another and therefore do not effect anydeformation of the threaded cylinder. It must furthermore be mentionedthat the flattened shape of the ring nose 80 of the die, whose radialextent is approximately the same in size as the radial extent of thering recess 22, has a further special advantage. It is possible withthis shape to move a relatively large volume of sheet metal materialwith a relatively small height of the ring nose above the planar surfaceof the die that engages around, and indeed such that the ring recess 22can be completely filled. A height of the ring nose above thesurrounding end surface of the die of approximately 0.8 mm or less,preferably 0.5 mm, is sufficient for this purpose. In another respect,the ring nose 80 provides that the slug 66 is cleanly separated from theremaining sheet metal material without the rivet section 20 having toproject out of the lower plane of the sheet metal part 14, but remainsset back by approximately 0.2 mm.

Due to the fact that the perforated die 42 contacts the sheet metalmaterial 14 over its planar circular ring-shaped end surface 84, thesheet metal material that surrounds the punched hole 70 produced by thepunching out of the panel slug 66 cannot be laterally or radiallydisplaced. A compression stress can rather be built up over the planarend surface 84 of the ring nose 80 of the perforated die 42 that is usedin the method in accordance with the invention in the sheet materialthat surrounds the punched hole 70 produced by the punching out of thepanel slug 66 until the material exceeds the flow limit and starts toflow plastically such that it not only penetrates into the ring recess22 at continued pressure, but rather produces a constriction 49 that isadjacent thereto in the rivet section 20 of the rivet element 10 andthat is then covered by the sheet metal material. Due to thisconstriction 49, the undercut 47 produced by the compression of therivet section 20 is increased therein—provided it has formed—whereby therivet element 10 is particularly reliably secured against being pressedout at the sheet metal part 14. Not only high bearing stresses are inparticular produced between the sheet metal part 14 and the rivetelement 10 that also contribute to security against rotation by thematerial that is located in the construction 49; a shape matching israther also produced such that the pressing of the rivet element 10 outof the sheet metal part 14 in the pressing-out direction is not possibleor is only possible on the application of substantial destructiveforces.

It must be noted at this point that the method in accordance with theinvention works while using a rivet element that is, however, notdeformed or is only slightly deformed within the framework of theapplication of the invention. The rivet element, preferably an RND rivetelement, is therefore used as a force fitting element since primarilyonly the sheet metal part is deformed.

1. A method of attaching a functional element to a sheet metal part ofsheet metal material, wherein the functional element has a head parthaving a ring-shaped support surface and a tubular shaft part that isformed as self-piercing and that extends at the side of the supportsurface of the head part and away from the head part, wherein thesupport surface comprises a ring recess, and wherein the sheet metalpart is supported on a perforated die that has a bore whose diameter atleast substantially corresponds to the outer diameter of the shaft partor is somewhat larger than it, wherein the bore is surrounded at theside of the perforated die facing the sheet metal part by a ring nosethat is raised with respect to a support surface of the perforated dieand defines a planar circular ring-shaped end surface, wherein thefunctional element is pressed onto the sheet metal part supported on theperforated die such that a panel slug is punched out of the sheet metalpart by means of the shaft part, wherein an undercut is produced at theshaft part on the attachment of the functional element to the sheetmetal part, and a portion of the sheet metal material that surrounds thepunched hole generated by the punching out of the panel slug isplastically pressed by means of the circular ring-shaped end face of thering nose into the ring recess while completely filling it, and ispressed in the region of the transition from the head part into theshaft part radially into the shaft part and is further pressed into theundercut formed during the attachment process.
 2. The method inaccordance with claim 1, wherein the sheet metal part has a thickness ofmore than 3 mm.
 3. The method in accordance with claim 1, whereinfeatures providing security against rotation are provided that arelocated in the region of the ring recess and/or in the region of thetransition of the ring recess into the shaft part and that selectivelydivide the ring recess into individual fields distributed about thelongitudinal axis of the functional element.
 4. The method in accordancewith claim 3, wherein a portion of the sheet metal material thatsurrounds the punched hole generated by the punching out of the panelslug is plastically pressed by means of the circular ring-shaped endface of the ring nose into the individual fields.
 5. The method inaccordance with claim 3, wherein the features providing security againstrotation are security against rotation noses.
 6. The method inaccordance with claim 1, wherein the undercut formed on the attachmentof the functional element to the sheet metal part is present in the formof one of a crease and a constriction.
 7. The method in accordance withclaim 1, wherein the rivet shaft part is free of undercuts prior to theattachment of the functional element to the sheet metal part.
 8. Themethod in accordance with claim 1, wherein the undercut is formed in theregion of the transition from the ring recess to the shaft part.
 9. Themethod in accordance with claim 1, wherein, during the punching of thesheet metal part, the ring nose also presses via its circularring-shaped end surface toward the lower side of the sheet metal partand there forms a recess that extends around the shaft part in theregion of its free end, wherein the material displaced by the formationof the recess is pressed into the undercut formed at the shaft partduring the attachment process.
 10. The method in accordance with claim9, wherein the material displaced by the formation of the recessenlarges the undercut formed during the attachment of the functionalelement to the sheet metal part.
 11. The method in accordance with claim1, wherein the functional element is pressed onto the sheet metal partsupported on the perforated die such that a portion of the sheet metalmaterial that surrounds the punched hole produced by the punching out ofthe panel slug starts to flow plastically as a result of contact withthe circular ring-shaped end surface of the ring nose and is plasticallypressed into the ring recess while completely filling it.
 12. The methodin accordance with claim 1, wherein the functional element is pressedonto the sheet metal part supported on the perforated die such that aportion of the sheet metal material that surrounds the punched holeproduced by the punching out of the panel slug is pressed radially intothe shaft part in the region of the transition from the head part intothe shaft part.
 13. The method in accordance with claim 1, wherein aperforated die is used as the perforated die whose circular ring-shapedend surface of the ring nose has a radial extent that corresponds toapproximately half the thickness of the sheet metal part and/or that issmaller than the radial extent of the ring recess, but larger than halfthe radial extent of the ring recess.
 14. The method in accordance withclaim 1, wherein a perforated die is used as the perforated die whosering nose has a volume that substantially corresponds to volume of thering recess of the functional element.
 15. The method in accordance withclaim 1, wherein a larger portion of sheet metal material of the sheetmetal part is deformed than material of the shaft part of the functionalelement on attachment of the functional element to the sheet metal part.